GPI, the Gemini Planet Imager

Introduction

The goal of these pages is to allow PIs to understand enough of the instrument's capabilities, expected modes,
performance etc. to propose projects which could be accomplished with the instrument
given its anticipated performance. We provide some detail on the instrument's internal configurations but
mainly concentrate on performance aspects. If in any doubt when writing a proposal, please contact the instrument scientist.

Overview of GPI's
capabilities

The instrument is at the last Commisioning stages and thus the actual performance is lower than the expected theorethical values for now. Any user of the instrument should check the latest news on the performance on the Status and Availabilitypage with details on Instrument Performancepage. The team is regularly updating the performance data as soon as the data are processed, by subscribing to the GPI News Email Exploder a user can be kept updated as any changes occur on these pages.

GPI
is an extreme adaptive-optics imaging polarimeter/integral-field spectrometer,
which will provide diffraction-limited data between 0.9 and 2.4 microns. The system will provide
contrast ratios of 10^6 on companions at separations of 0.2-1 arcsecond in a
1-2 hour observation. The science instrument will provide spectroscopy or dual-beam polarimetry of any
object in the field of view. Bright natural guide stars (I<9 mag) are required for optimal
performance of the GPI adaptive optics system. GPI will be capable of detecting
point sources down to H = 20 mag., with ≥ 5-sigma, in 1 hour (absent photon noise from
a bright companion). For more information on achievable contrast, see the
Contrast Page.

GPI combines four
main optomechanical systems:

The adaptive
optics (AO) system, responsible for fast measurement of the instantaneous wave
front, and for providing wave front control via two deformable mirrors.

The
calibration unit (CAL) is a high-accuracy infrared wave front sensor tightly
integrated with the coronagraph. It provides precise and accurate measurements
of the time-averaged wave front at the science wavelength and coronagraph focal
plane, to suppress persistent speckles caused by quasi-static wave front errors
in the final image. It also provides pointing and focus sensing to keep the
target star centered on the coronagraph with 1mas accuracy and slow low to
high-order aberration corrections.

The
coronagraph uses a combination of apodized masks and focal-plane stops to control diffraction and pinned speckles.

The integral
field spectrograph produces the final science image, including simultaneous multiple channels to suppress residual speckle noise in the spectroscopy mode or polarimetric imaging allowing the determination of the four Stokes
parameters.

The primary data product of the IFS is a data cube consisting of slightly more than 200x200 spatial locations, each with typically
18 spectral channels in spectroscopy mode and two spots in each positions for the polarimetric mode. The final field of view (FOV) is 2.8 arcseconds on a side, with 14 milliarcsecond sampling. A figure showing the expected format of data on the detector is given here.

The Instrument
Scientist for GPI is Fredrik Rantakyrö.

How to use these pages

The GPI pages are organized as follows (pages active at the time of the Call for Campaign Proposals
are in boldface):